Can the GeForce RTX 5090 run gpt-oss-20b?
Fits comfortably at Q4_K_M.
gpt-oss-20b is 21B parameters (MoE; all experts resident). At Q4_K_M the weights are about 11.7 GiB; with the 1.5 GiB runtime reserve that is 13.2 GiB against the card's 32GB, leaving about 18.8 GiB for context.
All three quants
32GB card| Quant | Weights | With reserve | Verdict | Headroom |
|---|---|---|---|---|
| Q4_K_Mthe everyday quant | 11.7 GiB | 13.2 GiB | Fits comfortably | 18.8 GiB |
| Q8_0near-lossless | 20.7 GiB | 22.2 GiB | Fits comfortably | 9.8 GiB |
| FP16full weights | 39.1 GiB | 40.6 GiB | Only with CPU offload | short 8.6 GiB |
Verdict rules: fits comfortably when weights plus reserve sit within 85% of VRAM; tight when they fit with little left for context; CPU offload when they exceed VRAM by up to 2x (runs, slowly, with layers in system RAM); no beyond that. The KV cache per token depends on the model's architecture and is not modelled here.
The numbers for this pairing
At Q4_K_M the weights take about 11.7 GiB; with the 1.5 GiB we set aside for the runtime that is 13.2 of the card's 32 GB, leaving about 18.8 GB for the context cache.
The highest-quality version that fits entirely in memory is Q8_0.
It is a mixture-of-experts model: about 3.6B of its 21B parameters work on each token, which helps speed, but all of them still have to fit in memory.
The cheapest card on our list that runs it comfortably at Q4 is the Radeon RX 9060 XT 16GB at about $530, against about $6,500 for this card.
At about $6,500, this card costs roughly $203 per GB of VRAM.
Running it at its full 575 W board power for 4 hours a day would use about 69 kWh a month, about $12.70 at the US average residential rate of 18.4 cents per kWh (2026-05); real use sits below that ceiling.
Prices are the lowest current listings our tracker saw on Oct 7, 2026, since averages include premium variants; launch prices are marked where we have no listing.
Good match. Get the card.
The GeForce RTX 5090 clears gpt-oss-20b at Q4_K_M and at Q8_0. Live listings below; this page was rebuilt 2026-10-07.
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About the model
gpt-oss-20b by OpenAI: 131,072-token native context, text, released 2025 under the Apache-2.0. Model card → · Hosted pricing on PicksByModel →